In general, an internal combustion engine is required to have an ignition position controlled in accordance with revolution number of the engine. For example, as shown in FIG. 1, a four cycle internal combustion engine is required to have such an advance characteristic that it is ignited at a substantially constant ignition angle or position .theta..sub.1 for an idling revolution N.sub.o (r.p.m.) to a setting revolution N.sub.i (r.p.m.) and that it is ignited with an advancing angle width .theta..sub.w of .theta..sub.1 to .theta..sub.2 of the ignition position in a middle and high revolution of the engine. In this figure, T.D.C. designates an upper dead point of a piston of the engine while B.T.D.C. designates a lower dead point of the engine piston. There have been proposed various ignition systems having such an advance characteristic. One of them is adapted to initiate to charge a capacitor at a given revolution angle of the engine, then to initiate to discharge the capacitor at a reference angle position with the discharging current controlled on the revolution number of the engine, and to ignite the engine at a position where the voltage across the capacitor is lowered to a given value. However, since the charge and discharge of the capacitor are controlled on the revolution number of the engine, respectively, the system is disadvantageously complicated.